1. Field of the Invention The present invention relates to face masks and in particular to a face mask forming a disposable filter respirator with an inner molded face flange and inhalation/exhalation valves.
2. Description of the Prior Art In the prior art, disposable face masks have been constructed, in their simplest form, of a layer of material, such as fiberfill material which layer forms both the filter material itself and the support to position the mask over the nose and mouth of a user. The mask is typically held in position by elastic straps which are attached at the sides of the mask and extend around the back of the head.
Other disposable face masks have been constructed of layers of fiberfill material supporting a separate layer of filter material, such as a layer of filter material supported between two outer layers or by a single layer of fiberfill material Other types of disposable face masks have used other materials to form the support surface, such as the use of an openwork plastic material forming a self-supporting net to hold and support the filter material. These more complicated structures include a self supporting layer to provide for a better fit of the mask against the face of the user when the mask is held in place by the elastic straps.
Two problems which occur with the use of any face mask are: (1) a proper fit of the face mask to the face of the user so as to eliminate as much as possible, any passage of air to the user before it has passed through the filter material and (2) a heat and moisture buildup which can occur within the mask, especially if the user of the mask is engaging in strenuous work. It can be seen that these two problems are somewhat interrelated since it is desirable to provide for a good fit of the mask to the face of the user and the better the fit, the tighter the seal and the more the problem of heat and moisture buildup. This is because if the fit is not proper, then exhaled air, including heat and moisture can leak around the edge of the mask to the exterior. However, an improper fit can be dangerous since if exhaled air can leak out, inhaled air can leak in and as indicated above, all inhaled air should pass through the filter material.
One solution to the problem of heat and moisture buildup within the mask is the use of an exhalation valve located within the mask. For example, reference is made to prior U.S. Pat. No. 4,454,881 having the same inventors as the present application and with this patent disclosing a disposable filter mask having an exhalation valve. In addition, this patent discloses the use of a sealing bead located around the peripheral edge of the mask to provide an edge seal between the mask and the face of the user and additionally including membrane portions extending from the bead member to enhance the fit of the mask at least in the areas of the sides of the nose and the upper cheekbone of the user.
Although the mask shown in U.S. Pat. No. 4,454,881 is an improvement over prior disposable face masks, it still has some deficiencies. Specifically, it is desirable to provide for an ever better fit of the mask to the face of the user and to provide for a check of this fit and further to channel inhaled air more directly to the nose area of the user and to direct the exhaled air out of the mask to more completely eliminate the problem of heat and moisture buildup.
There have been other prior art attempts to solve the above described problems. For example, reference is made to U.S. Pat. No. 4,630,604 listing Edward N. Montesi as the inventor which patent discloses an inhalation/exhalation valve assembly for a disposable filter respirator. The Montesi patent describes a respirator having a disposable filter and includes a valve having a central aperture providing concentric inhalation and exhalation valves. The filter structure of the Montesi patent is generally formed from relatively rigid molded plastic members supporting a filter material and with an inner 0 rubberlike face piece of the type well known in the art providing for the sealing of the mask to the face of the user. The Montesi respirator, although providing for a good seal of the mask to the face of the user and also providing for the substantial elimination of heat and moisture buildup, suffers from a number of deficiencies. First, the mask is relatively expensive to make since it is formed from relatively rigid molded plastic members which are expensive to manufacture and difficult to assemble. Second, the mask is somewhat cumbersome because of its large size and rigid construction.